Liquid source vaporizer

ABSTRACT

The present invention is one that is intended to prevent bubbles from being recombined to suppress the bubbles from being enlarged, and also homogenize a temperature distribution of a stored liquid source, and provided with: a liquid source container; a first heater that is provided on a side wall of the liquid source container and intended to heat the stored liquid source to a predetermined temperature; a second heater that is provided in an inside central part of the liquid source container and intended to heat the stored liquid source to the predetermined temperature; a plurality of bubble generators that are immersed into the stored liquid source, provided between the second heater and the side wall, and release carrier gas into the liquid source to perform bubbling; and a gas supply pipe that supplies the carrier gas to the bubble generators.

TECHNICAL FIELD

The present invention relates to a liquid source vaporizer thatvaporizes a liquid source by a bubbling method using carrier gas.

BACKGROUND ART

As this sort of liquid source vaporizer, for example, as disclosed inPatent literature 1, there is one that is provided with: a liquid sourcecontainer that stores a liquid source; a carrier gas introduction pipethat is intended to bubble the liquid source stored in the liquid sourcecontainer with use of carrier gas; and a bubbling gas output pipe thatis connected to an upper space (gas phase) of the liquid sourcecontainer and intended to supply gas, which is obtained by the bubbling,to an outside of the liquid source container. Also, a tip part of thecarrier gas introduction pipe is immersed into the liquid source, andconnected with bubbling nozzles constituted of a plurality of thintubes. As bubbles generated by the bubbling nozzles float in the liquidsource, the liquid source is vaporized into the bubbles, and thereby thevaporized source is supplied outside together with the carrier gas.Also, this vaporizer is configured such that, on an outer surface of theliquid source container, a heater for heating the stored liquid sourceto a constant temperature is provided to make the liquid source have ahomogenized temperature distribution.

However, there is a problem that the bubbles generated by the bubblingnozzles attach to an inner surface of the liquid source container orcomponents inside the container, and this causes the bubbles to berecombined with one another, thereby enlarging the bubbles. If thebubbles are enlarged as described, a ratio of the liquid source that isvaporized into the bubbles is decreased, and the liquid source cannot besaturated in the bubbles, which reduces vaporization efficiency.

Also, if the liquid source container is large-sized, there occurs aproblem that a migration area of the bubbles generated by the bubblingnozzles is limited to part of the container, so that a stirring effecton the liquid source by the bubbles is not obtained, and therefore it isdifficult to keep a temperature distribution of the liquid sourcehomogenized. In addition, if the liquid source container is increased insize, there also occurs a problem that, by only providing the heater onthe outer surface of the liquid source container, it is not easy to heatthe liquid source such that it has a homogenized temperaturedistribution. It is also thought that by providing the bubbling nozzlessuch that the bubbles hit against the inner surface of the liquid sourcecontainer, the liquid source is stirred; however, as described above,there occurs the problem that the bubbles attach to the inner surface ofthe liquid source, and this causes the bubbles to be recombined with oneanother, thereby enlarging the bubbles.

CITATION LIST Patent Literature

Patent literature 1: Japan patent laid-open number 06-267852

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Therefore, the present invention is made to solve the above problems atonce, and has a main desired object to prevent bubbles from beingrecombined to suppress the bubbles from being enlarged, and also tohomogenize a temperature distribution of a stored liquid source.

Solution to Problem

That is, a liquid source vaporizer according to the present invention isprovided with: a liquid source container that is configured to store aliquid source; a first heater that is provided on at least a side wallof the liquid source container and is configured to heat the storedliquid source; a second heater that is provided inside the liquid sourcecontainer and is configured to heat the stored liquid source; aplurality of bubble generators that are configured to immerse into thestored liquid source, provided between the second heater and the sidewall, and are configured to release carrier gas into the liquid sourceto perform bubbling; and a gas supply pipe that is configured to supplythe carrier gas to the bubble generators.

If so, on the side wall and in an inside central part of the liquidsource container, the first and second heaters are respectivelyprovided, and therefore a temperature distribution of the liquid sourcestored in the liquid source container can be easily homogenized. Also,the bubble generators are provided between the second heater and a sidewall inner surface, and therefore bubbles can be prevented from easilycoming into contact with the second heater and side wall inner surface,and also from being enlarged by the attachment of the bubbles to them.Further, convection can also be formed in the liquid source container tothereby stir the liquid source. Still further, by providing theplurality of bubble generators, even if the liquid source container islarge-sized, a stirring effect on the liquid source can be sufficientlyproduced by the bubbles generated by the respective bubble generators,and thereby the temperature distribution of the stored liquid source canbe easily homogenized.

The plurality of bubble generators are provided such that the bubblesgenerated by the plurality of bubble generators pass in the vicinity ofthe side wall inner surface of the liquid source container and in thevicinity of the second heater, and therefore the temperaturedistribution of the liquid source can be further homogenized by thebubbles generated by the bubble generators while preventing the bubblesfrom being easily attached to the side wall inner surface of the liquidsource container and second heater. The vicinity of the second heaterrefers to a temperature gradient region generated between the secondheater and the liquid source, and a location that, in a state where thebubbles are generated, just enables an influence due to the attachmentof the bubbles to the second heater to be substantially ignored. Thevicinity of the side wall inner surface refers to a temperature gradientregion generated between the side wall inner surface and the liquidsource, and a location that, in the state where the bubbles aregenerated, just enables an influence due to the attachment of thebubbles to the side wall inner surface on vaporization efficiency or thelike to be substantially ignored.

Also, in order to further homogenize the temperature distribution of theliquid source, the plurality of bubble generators are desirably providedradially around a central axis of the liquid source container at regularintervals.

In order to homogenize the temperature distribution of the liquid sourcewith accuracy by making bubbles generated by the respective bubblegenerators constant, desirably, the plurality of bubble generators areones having the same configuration, and the gas supply pipe is providedwith a constant flow rate device that is intended to supply the carriergas having a constant flow rate to the plurality of bubble generators.

Advantageous Effects of the Invention

According to the present invention configured as described, the bubblescan be prevented from being recombined to suppress the bubbles frombeing enlarged, and also a temperature of the liquid source stored inthe liquid source container can be homogenized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall configuration diagram of a liquid source vaporizeraccording to one embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating an arrangement mode of bubblegenerators of the same embodiment.

FIG. 3 is a diagram illustrating a temperature distribution of a liquidsource between a side wall inner surface and a second heater.

FIG. 4 is cross-sectional view illustrating a branch pipe and a pipefitting of the bubble generator of the same embodiment.

FIG. 5 is a diagram schematically illustrating a liquid source vaporizeraccording to a variation.

REFERENCE CHARACTERS LIST

100: Liquid source vaporizer

2: Liquid source container

3: First heater

4: Second heater

5: Bubble generator

6: Gas supply pipe

DESCRIPTION OF EMBODIMENTS

One embodiment of a liquid source vaporizer according to the presentinvention will hereinafter be described with reference to the drawings.

A liquid source vaporizer 100 according to the present invention is onethat vaporizes, on the basis of a bubbling method, a liquid sourceserving as a deposition source for a deposition apparatus using a CVDmethod or the like, and supplies the vaporized source to the depositionapparatus, and as illustrated in FIG. 1, is provided with: a liquidsource container 2 that stores the liquid source such astetraethoxysilane (TEOS); first heaters 3 that are provided on a sidewall, an upper wall, and a lower wall of the liquid source container 2,and intended to heat the stored liquid source to a predeterminedtemperature; a second heater 4 that is provided in an inside centralpart of the liquid source container (tank) 2, and intended to heat thestored liquid source to the predetermined temperature; a plurality ofbubble generators 5 that are immersed into the stored liquid source,provided between the second heater 4 and the side wall, and releasecarrier gas into the liquid source to perform bubbling; and a gas supplypipe 6 that supplies the carrier gas such as nitrogen or argon to thebubble generators 5.

The liquid source container 2 is an airtight container that is of asubstantially rotational body shape and made of stainless steel, and anupper space (air phase) formed in a state where the liquid source isstored is connected with a gas lead-out pipe 7 for supplying vaporizedliquid source after the bubbling together with the carrier gas to adeposition apparatus (not illustrated). Note that FIG. 1 illustrates adiagram in which the gas lead-out pipe 7 is connected to the upper wallof the liquid source container 2.

The first heaters 3 are provided in contact with or close to entireouter surfaces of the side wall, upper wall, and lower wall of theliquid source container 2. Also, the second heater 4 is provided in theinside central part of the liquid source container 2 so as to extend inan up-and-down direction and be supported by the upper wall. Inaddition, the first heaters 3 and the second heater 4 are, in order toheat the liquid source to the predetermined temperature (e.g., 50° C.),elevated in temperature to the same temperature (e.g., 50° C.) by anunillustrated control part.

Each of the bubble generators 5 is one that releases the carrier gasinto the liquid source to form a number of bubbles each having apredetermined diameter, and configurations of the respective bubblegenerators 5 are the same. The diameter of the bubble is one thatdepends on a floating distance and just enables the liquid source to bevaporized and saturated into the bubble, and may be, for example,approximately 1 mm. Also, a flow rate of the carrier gas supplied to thebubble generators 5 is determined by an after-mentioned mass flowcontroller (MFC) 8 and a constant flow rate device.

Also, the bubble generators 5 are provided in the vicinity of a bottompart of the liquid source container 2, and specifically, provided on alower side of the second heater 4 so as to be positioned on a diameterdirection outer side of the second heater 4. More specifically, thebubble generators 5 are provided such that the bubbles generated by thebubble generators 5 pass in the vicinity of a side wall inner surface ofthe liquid source container 2 and in the vicinity of the second heater4. In the present embodiment, the bubble generators 5 are, asillustrated in FIG. 2, provided, between the second heater 4 and theside wall of the container 2, in ranges from the vicinity of the secondheater 4 to the vicinity of the side wall of the container 2. That is,the bubble generators 5 are provided so as not to, in verticalprojection, mutually overlap with the second heater 4 or the container 2side wall. Further, the bubble generators 5 are, as illustrated in FIG.2, provided radially around a central axis C of the liquid sourcecontainer 2 at regular intervals.

Note that, as illustrated in FIG. 3, the vicinity of the second heater 4refers to a temperature gradient region (“a second heater sidetemperature gradient region” in FIG. 3) generated between the secondheater 4 and the liquid source, and a location that, in a state wherethe bubbles are generated, just enables an influence due to theattachment of the bubbles to the second heater 4 to be substantiallyignored. The vicinity of the side wall inner surface refers to atemperature gradient region (“a side wall side temperature gradientregion” in FIG. 3) generated between the side wall inner surface and theliquid source, and a location that, in the state where the bubbles aregenerated, just enables an influence due to the attachment of thebubbles to the side wall inner surface on vaporization efficiency or thelike to be substantially ignored. Each of the temperature gradientregions refers to a region where, at a liquid level of the liquid sourceor at a predetermined depth in the liquid source, a temperature of theliquid source is changed with horizontally increasing distance from theheater 3 or 4. Note that FIG. 3 illustrates a temperature distributionof the liquid source at a predetermined depth X and correspondingtemperature gradient regions.

The temperature gradient region generated between the second heater 4and the liquid source is different between operation start time of thesecond heater (heating start time) and heating stability time, and thetemperature gradient region at the heating stability time is narrowerthan that at the operation start time. Accordingly, in order to bringthe bubble generators 5 as close to the second heater 4 as possible, oneend of each of the bubble generators 5 is preferably provided within thetemperature gradient region generated between the second heater 4 andthe liquid source at the heating stability time. Also, the temperaturegradient region generated between the side wall inner surface and theliquid source is different between operation start time of the firstheaters 3 (heating start time) and heating stability time, and thetemperature gradient region at the heating stability time is narrowerthan that at the operation start time. Accordingly, in order to bringthe bubble generators 5 as close to the side wall inner surface aspossible, the other ends of the bubble generators 5 are preferablyprovided within the temperature gradient region generated between theside wall inner surface and the liquid source at the heating stabilitytime.

The gas supply pipe 6 is provided by being inserted inside through theupper wall of the liquid source container 2, and in the presentembodiment, provided along the second heater 4. Specifically, the gassupply pipe 6 is provided by being inserted inside through the upperwall of the liquid source container 2, and includes: one main pipe 61that extends along the second heater 4 to below a lower end of thesecond heater 4; and a plurality of branch pipes 62 that are formed bybranching the main pipe 61 at a lower end of the main pipe 61 and extendin radial directions of the liquid source container 2.

The main pipe 61 is provided such that a pipe axis thereof issubstantially parallel to the central axis C of the liquid sourcecontainer 2, and branched such that the branch pipes 62 are providedradially in directions substantially orthogonal to the pipe axis of themain pipe 61 and also at the regular intervals in the radial directions.Also, tips of the branch pipes 61 are connected with the bubblegenerators 5, respectively. That is, the gas supply pipe 6 is configuredto be branched on a lower side of the lower end of the heater 4. Inaddition, the main pipe 61 is provided with: the mass flow controller(MFC) 8 for controlling a flow rate of the carrier gas; and a preheater9 for preheating the carrier gas.

As described, an upper side of the bubble generators 5 is configuredsuch that piping only including the main pipe 61 is present, so that apiping configuration on the upper side of the bubble generators 5 can besimplified, and the bubbles generated by the bubble generators 5 can besuppressed from coming into contact with the piping as much as possible.

Also, each of the branch pipes 62 and corresponding bubble generator 5are, as illustrated in FIG. 4, connected to each other through a pipefitting 10 such as a VCR fitting. Also, by decreasing an openingdiameter of an annular metallic sealing material (gasket) 11 providedinside the pipe fitting 10, an orifice serving as the constant flow ratedevice is configured. The pipe fittings 10 between the respective branchpipes 62 and the corresponding bubble generators 5 have the sameconfiguration, and the sealing materials 11 inside the pipe fittings 10also have the same configuration. On this basis, supply flow rates ofthe carrier gas supplied to the respective bubble generators 5 areconfigured to be the same.

<Effects of the Present Embodiments>

According to the liquid source vaporizer 100 configured as describedaccording to the present embodiment, the first heater 3 and the secondheater 4 are respectively provided on the side wall and in the insidecentral part of the liquid source container 2, and therefore atemperature distribution of the liquid source stored in the liquidsource container 2 can be easily homogenized. Also, the bubblegenerators 5 are provided between the second heater 4 and the side wallinner surface, and therefore the bubbles can be prevented from easilycoming into contact with the second heater 4 and side wall innersurface, and also from being enlarged by the attachment of the bubblesto them. Further, by providing the plurality of bubble generators 5,even if the liquid source container 2 is large-sized, a stirring effecton the liquid source can be sufficiently produced by the bubblesgenerated by the respective bubble generators 5, and thereby thetemperature distribution of the stored liquid source can be easilyhomogenized.

<Other Embodiments>

Note that the present invention is not limited to the above-describedembodiment.

For example, in the above-described embodiment, the carrier gas supplypipe is configured to have the one main pipe and the plurality of branchpipes; however, the present invention may be configured such that,without branching the carrier gas supply pipe, each of the bubblegenerators is provided with one carrier gas supply pipe. Also, thepresent invention may be configured such that a plurality of bubblegenerators are treated as a group, and the same carrier gas supply pipeas that in the above-described embodiment is provided for each group.

Also, a connecting position of the carrier gas supply pipe is notlimited to the upper wall of the liquid source container, but may be theside wall or the lower wall.

Further, in the above-described embodiment, the constant flow ratedevice provided for each of the branch pipes of the carrier gas supplypipe is configured with use of the sealing material provided inside theVCR fitting; however, besides, the constant flow rate device may beprovided on each of the branch pipes.

In addition, as illustrated in FIG. 5, the present invention may beconfigured such that, in a state where a plurality of bubble generatorsare treated as a group, a carrier gas supply pipe 6A or 6B is providedfor each group, and switching valves V are provided for the respectivesupply pipes 6A and 6B, the liquid source is vaporized with switchingbetween the supply pipes 6A and 6B. In this case, the present inventionis configured such that a pressure sensor P that measures a pressureinside each of the supply pipes 6A and 6B is provided, and if a pressureinside one of the supply pipes in use is increased to a predeterminedvalue or more, on the assumption that there is a problem of clogging ofany of the bubble generators 5, the supply pipe is switched to the othersupply pipe to thereby generate bubbles. Note that FIG. 5 illustrates aconfiguration in which the respective carrier gas supply pipes 6A and 6Bmerge on an upstream side, and at a point of the merging, the pressuresensor P is provided to measure a pressure. If so, in the case where aproblem occurs, such as clogging of a bubble generator provided for oneof the carrier gas supply pipes, by switching the carrier gas supplypipe to the other carrier gas supply pipe, long-term operation can beperformed.

The liquid source vaporizer in the above-described embodiment isconfigured to use the plurality of bubble generators; however, besides,the liquid source vaporizer may be configured to use one ring-like(e.g., annular) bubble generator to surround the second heater.

In addition, the above-described embodiment has the four bubblegenerators; however, the number of bubble generators can beappropriately changed depending on a flow rate of the carrier gas, or aconfiguration of the liquid source container, such as a size or a shape.

Further, the above-described embodiment is adapted to radially providethe bubble generators at the regular intervals; however, an arrangementmode of the bubble generators can be appropriately changed depending ona configuration inside the liquid source container.

Also, even if the liquid source vaporizer in the above-describedembodiment does not have the second heater 2, it can vaporize the liquidsource; however, if the liquid source container is increased in size,vaporization efficiency is reduced. On the other hand, if the liquidsource container is small-sized, the liquid source can be sufficientlyvaporized only with the first heaters. That is, in the case where theliquid source container is small-sized, the liquid source vaporizer isdesirably configured to be provided with: a liquid source container thatstores a liquid source; a heater that is provided on at least a sidewall of the liquid source container and intended to heat the storedliquid source; a plurality of bubble generators that are immersed intothe stored liquid source and intended to release carrier gas into theliquid source to perform bubbling; and a gas supply pipe that suppliesthe carrier gas to the bubble generators, wherein the plurality ofbubble generators are provided such that bubbles generated by theplurality of bubble generators pass in a vicinity of a side wall innersurface of the liquid source container.

Furthermore, it should be appreciated that the present invention is notlimited to any of the above-described embodiments, and can be variouslymodified without departing from the scope thereof.

INDUSTRIAL APPLICABILITY

According to the present invention, bubbles can be prevented from beingrecombined to suppress the bubbles from being enlarged, and also atemperature of a liquid source stored in a liquid source container canbe homogenized.

1. A liquid source vaporizer comprising: a liquid source container thatis configured to store a liquid source; a first heater that is providedon at least a side wall of the liquid source container and is configuredto heat the stored liquid source; a second heater that is providedinside the liquid source container and is configured to heat the storedliquid source; a plurality of bubble generators that are configured toimmerse into the stored liquid source, provided between the secondheater and the side wall, and are configured to release carrier gas intothe liquid source to perform bubbling; and a gas supply pipe that isconfigured to supply the carrier gas to the bubble generators.
 2. Theliquid source vaporizer according to claim 1, wherein the plurality ofbubble generators are provided such that bubbles generated by theplurality of bubble generators pass in a vicinity of a side wall innersurface of the liquid source container and in a vicinity of the secondheater.
 3. The liquid source vaporizer according to claim 1, wherein theplurality of bubble generators are provided radially around a centralaxis of the liquid source container at regular intervals.
 4. The liquidsource vaporizer according to claim 1, wherein the plurality of bubblegenerators are ones having a same configuration, and the gas supply pipeis provided with a constant flow rate device that is configured tosupply the carrier gas having a constant flow rate to the plurality ofbubble generators.